Mechanism for cutting a sheet

Abstract

A mechanism for cutting a sheet of paper includes a rotary blade and a counter blade. The periphery of the counter blade is substantially flush with a paper-setting surface on one side of a stand portion of a cutter frame. The axis of the counter blade is disposed forwardly of the axis of the rotary blade. The rotary blade and counter blade are stored in a blade stand. The cutter frame supports the blade stand for forward movement and the subsequent rearward movement. The cutter frame is provided with a driver including pulleys and a wire. The driver moves the blade stand along the stand portion of the frame.

What is claimed is: 
     
       1. A mechanism for cutting a sheet, comprising: a frame having a stand portion that has on one side a flat surface adapted to support a sheet to be cut;   a blade stand supported by said frame for a forward movement and a subsequent reverse movement along said stand portion;   a circular rotary blade supported by said blade stand for rotation about a rotary blade axis, said rotary blade axis located above a plane defined by said flat surface of said stand portion;   a circular counter blade supported by said blade stand for rotation about a counter blade axis, said counter blade axis located below the plane defined by said flat surface of said stand portion;   said rotary blade engaging said counter blade at a contact point,   said counter blade axis being disposed forwardly of said rotary blade axis with respect to the forward movement of the blade stand, and   means for rotating said rotary blade and said counter blade in response to the forward movement of said blade stand along said stand portion.   
     
     
       2. The mechanism as claimed in claim 1, wherein said means include a spring biasing said rotary blade into engagement with said counter blade at said contact point. 
     
     
       3. A mechanism for cutting a sheet, comprising: a frame having a stand portion that has on one side a flat surface adapted to support a sheet to be cut;   a blade stand supported by said frame for a forward movement and a subsequent reverse movement along said stand portion;   a circular rotary blade supported by said blade stand for rotation about a rotary blade axis, said rotary blade axis located above a plane defined by said flat surface of said stand portion;   a circular counter blade supported by said blade stand for rotation about a counter blade axis, said counter blade axis located below the plane defined by said flat surface of said stand portion;   said rotary blade engaging said counter blade at a contact point,   said counter blade axis being disposed forwardly of said rotary blade axis with respect to the forward movement of the blade stand, and   means for rotating said rotary blade and said counter blade in response to the forward movement of said blade stand along said stand portion; and   wherein said means include a side edge of said stand portion, which cooperates with said rotary blade to interpose said counter blade between said side edge and said rotary blade, and a spring biasing said rotary blade into frictional engagement with said counter blade at said contact point to urge said counter blade into frictional engagement with said side edge.   
     
     
       4. The mechanism as claimed in claim 3, wherein, viewing along said counter blade axis, said rotary blade overlaps said counter blade so that a periphery thereof intersects a periphery of said counter blade at a first intersection point and a second intersection point disposed forwardly of said first intersection point with respect to the forward movement of said blade stand, and wherein said contact point coincides with said second intersection point. 
     
     
       5. The mechanism as claimed in claim 4, wherein said rotary blade is disposed within a plane that forms a predetermined angle with a plane including a cutting section of the sheet. 
     
     
       6. The mechanism as claimed in claim 5, wherein said predetermined angle ranges from 0.5 degrees to 5 degrees. 
     
     
       7. The mechanism as claimed in claim 5, wherein said predetermined angle is approximately 3 degrees. 
     
     
       8. The mechanism as claimed in claim 6, wherein said counter blade is in the form of a disc with edge rounded. 
     
     
       9. The mechanism as claimed in claim 8, wherein said disc results from press-machining a sheet of metal. 
     
     
       10. The mechanism as claimed in claim 9, wherein the material of said counter blade is steel classified as a general purpose steel according to Japanese Industrial Standard (JIS). 
     
     
       11. The mechanism as claimed in claim 3, wherein said means includes a wheel connected to said rotary blade for unitary rotation, said wheel cooperating with said blade stand to interpose said stand portion between said wheel and a portion of said blade stand. 
     
     
       12. The mechanism as claimed in claim 11, wherein, during forward movement of said blade stand, said counter blade is subject to a moment occurring at the frictional engagement with said rotary blade and to a moment occurring at the frictional engagement with said side edge. 
     
     
       13. The mechanism as claimed in claim 3, wherein said blade stand includes: a first blade stand section, disposed above said flat surface on the one side of said stand portion, storing said rotary blade;   a second blade stand section, disposed below said flat surface, for storing said counter blade; and   an arm interconnecting said first and second blade stand sections;   said first blade stand section having, at a front end thereof, a first guide,   a second guide to which said first guide connects, and   a third guide to which said second guide connects.   
     
     
       14. The mechanism as claimed in claim 13, wherein said second blade stand section has a slope inclined away from said rotary blade and said counter blade. 
     
     
       15. The mechanism as claimed in claim 14, wherein said second blade stand section has, at a front end thereof, a front plow portion, said front plow portion sloping away from said stand portion from the front end of said second blade stand section towards a rear end thereof. 
     
     
       16. The mechanism as claimed in claim 14, wherein said blade stand has, at a rear end thereof, a rear plow portion, said rear plow portion sloping away from said stand portion from the rear end of said second blade stand section towards a front end thereof. 
     
     
       17. A mechanism as claimed in claim 14, wherein said first blade stand section is separable and includes a cartridge. 
     
     
       18. The mechanism as claimed in claim 3, wherein said side edge of said stand portion is perpendicular to said flat surface. 
     
     
       19. The mechanism as claimed in claim 3, wherein said counter blade has an outer periphery substantially flush with said flat surface on said stand portion. 
     
     
       20. The mechanism as claimed in claim 11, wherein said wheel connected to said rotary blade rotates about an axis parallel to said rotary blade axis.